This is essentially the same as the 3GB deals that have been posted on HUKD before, but this time its 12GB/12 Month SIM. I think this works out a bit more cost than 4x 3GB SIMs, but its more convenient having just one SIM.
I've cut mine down to Micro-SIM size, put it in an iPad and got a years worth of 3G browsing for £49 (or 12GB which-ever comes fist).
These work out much better than contract as there is no restriction on a per month basis - so one month you can use 1Gb, next month 4Gb if you so wish.
To clarify some of the questions in comments;
* Yes - It will allow tethering and can be used in phones, dongles, MiFi's and iPads.
* Yes - You can use it in an iPad - just buy a SIM Cutter from ebay - they are very reliable and perfect for deals such as this.
* It will last for 12 months from _first use_. You can then use _up to_ 12Gb of data across an up to 12 month period - its which ever comes first.
* It won't expire in non-active usage during its 12-month active period.